In general manufacturing of semiconductor devices, repetitious processes of film formation and pattern etching are provided on semiconductor wafers to manufacture intended devices. Every year the demands particularly for high specifications of the film formation technique are growing as semiconductor devices became highly densified and integrated, and further reduction in the thickness of the film has been required to form quite thin oxide films, such as insulating films and gate-insulating films in a capacitor in the device for example, in which high insulating ability is also required.
Silicon oxide films and silicon nitride films can be used for these insulating films, but more metal oxide films are recently chosen as material with better insulating properties. The metal oxide films, providing highly reliable insulating ability in spite of their thinness, can provide further improved insulating ability by applying modification processing on the surface after the metal oxide film formation is completed.
Metal nitride films are also more often adopted as material with favorable ability for barrier metal layers, etc. In association with the above-mentioned metal oxide films and metal nitride films, metallic compound material has come into wide use as a material gas at the film formation. The metallic compound material generally is liquid or solid at normal temperature and pressure, and has characteristics to be hardly evaporated or sublimed for its relatively low vapor pressure.
The gas supply system of a material gas produced from metallic compound material is hereinafter explained. FIG. 21 is a structural block diagram showing a conventional gas supply system of a material gas composed of metallic compound material.
As shown in FIG. 21, the metallic compound material M composed of liquid or solid organic metal material or the like is contained in a material reservoir tank 2 into which a carrier gas, e.g. Ar gas, is fed while a flow controller 4 controls the flow rate, thereby promoting evaporation or sublimation of the metallic compound material. The material gas produced by evaporation or sublimation of the metallic compound material is carried with the carrier gas to a processing apparatus 8 through a gas passage 6 and supplied into the processing apparatus 8 with other necessary gas in order to deposit a specific thin film on the surface of a semiconductor wafer W that is an object to be processed. In addition, a heater 10 may be provided at the material reservoir tank 2 as necessary so that evaporation of the metallic compound material is promoted.